[GSoC] coreboot for ARM64 Qemu – Week #4 and #5

From this week I started dealing with the core aspects of aarch64 design. I continued with the process of building the armv8, along with handling the required patching-up, interfacing, hook-ups. In my last post, I had talked about the toolchain building error (in binutils) for arm64 which I was facing on OSX. I had to remove the –enable-gold flag from the binutils. After making this small update, the build_BINUTILS looked like this, and I was able to get the toolchain working.

build_BINUTILS() {
 if [ $TARGETARCH == "x86_64-elf" ]; then
 CC="$CC" ../binutils-${BINUTILS_VERSION}/configure --prefix=$TARGETDIR \
 --target=${TARGETARCH} --enable-targets=${TARGETARCH}${ADDITIONALTARGET} \
 --disable-werror --disable-nls --enable-lto \
 --enable-plugins --enable-multilibs CFLAGS="$HOSTCFLAGS" || touch .failed
 $MAKE $JOBS || touch .failed
 $MAKE install DESTDIR=$DESTDIR || touch .failed

The work had just began after fixing the toolchain. On attempting to building, the faced error I got was :

toolchain.inc:137: *** building bootblock without the required toolchain. Stop.

This was due to certain wrongly configured CONFIG options in the Kconfig. After this stage the initial bring-up of arm64 looked stable. Moving forward, I was met with an error in src/arch/arm64/c_entry.c

src/arch/arm64/c_entry.c: In function ‘arm64_init’: src/arch/arm64/c_entry.c:52:2: error: implicit declaration of function ‘cpu_set_bsp’ [-Werror=implicit-function-declaration] cpu_set_bsp();

The inclusion of necessary files and structures were correct, and I kept getting this error. Furquan ultimately pointed to change 257370  following which, I could get past this. After this, I had to solve another BSD/OSX issue about date in genbuild_h.sh to get my build progressing.

Subsequently, some architectural decisions had to be made for the armv8. In the initial version, I had been banking on cbfs_media based structure in media.c, for creating functions for read, write and map. But the older formulation (in cbfs_core.c and cbfs_core.h) is changed now. In order to keep up, and to maintain uniformity, we decided to handle this as it is handled in armv7, i.e by creating a mapping to the qemu memory mapped space. Another point of discussion for stage loading. It is being brought up similar to armv7 for now. This might change in the future. Also the organisation for UART was finalised. plo11.c is included, as in  src/drivers/uart/Makefile.inc. by setting the DRIVERS_UART_PL011 in armv8 Kconfig.

Next hitch was dealing with SMP. In my proposal, I had suggested that incorporating smp into the emulation could be a long term goal. But since smp is a part of core arm64 logic, this cannot be completely ignored at this stage. I am met with this

coreboot/src/arch/arm64/stage_entry.S:94: undefined reference to `smp_processor_id’
build/arch/arm64/c_entry.romstage.o: In function `seed_stack’:


A cpu file which adds smp_processor_id() is needed at this moment, which I am currently working on. Next week’s plan is to get past these (and meet new unforeseen issues 😛 ) and boot off on qemu.